I stayed at this listing for about a month. Air is a delightful host, very prompt to reply to any issue that arose. The check-in process could have been a bit smoother (there were some issues with AC and internet) but Air made sure they got resolved in a prompt fashion. The apartment was very comfortable and clean. The bedroom and main living space are pleasant for a single-person stay. Kitchen was very tiny and bathroom could have been a little larger as well. I'd say that for one person, this apartment is good but if you're traveling with two or three people, it might be slightly tight.
The gym was really nice and I used it frequently. I didn't use the pool so can't comment on it. Some of the building staff were very smiley and friendly, others a bit less. Overall it was definitely an enjoyable stay. The one thing that prevents me from rating this listing as 5 stars really is its location. It's an 18-20 minute walk to either Phrom Phong or Asok station, so I ended up taking motor bikes almost every day. Fine if you enjoy motorbikes, but I got into an accident on one and had to spend a ton of money on damages and medical expenses, so I avoided taking bikes as much as possible during the second half of my stay. So to sum up, really clean and comfy apartment, but keep in mind that it's a bit of a hike to get to the BTS.